A FACS-Analyzer with electronic cell volume and wide angle light scatter analysis for two parameter identification of cell populations and simultaneous two color immunofluorescence detection in combination with the Consort 30 data management system and magnetic tape storage option for acquisition, storage and display of four-parameter correlated data is requested. This equipment will be used in support of 3 major NIH supported research projects. The studies of experimental leprosy in mangabeys, African green and rhesus monkeys emphasize the identification and characterization of functional lymphocyte subpopulations and their alteration during the development of lepromatous leprosy. Studies of the effects of vaccines and immunomodulation on the lepromatous disease process and on the functional lymphocyte subpopulations identified by immunofluorescent staining with combinations of monoclonal antibodies will be conducted. Studies of lyophilized antihemophilic factor VIII effects in rhesus, African green and squirrel monkeys related to the occurrence of the acquired immunodeficiency syndrome (AIDS) in hemophiliacs also emphasize the identification and characterization of monkey lymphocyte subsets and the effects of factor VIII in vivo and in vitro. Both the leprosy and the AIDS research projects also involve the study of the relationship of functional lymphocyte subpopulations to annual rhythmic variations in lymphocyte responsiveness that we have observed in monkeys. The understanding of the physiologic basis of these cyclic changes in immune function must be considered in interpretation of experimental results and could have important implications for our understanding of chronic infectious processes and variations in individual susceptibility to infectious disease. The studies of pyelonephritis in cynomolgus and African green monkeys emphasize the detection of adherence receptors for bacterial fimbriae on cells of the urogenital tract by binding of fluorochrome labeled bacteria and bacterial components. The identification of factors affecting the density of these receptors related to individual susceptibility to recurrent or chronic urinary tract infections could be an important adjunct to therapy, prognosis and prevention of pyelonephritis. The FACS-Analyzer is essential for the successful completion of these studies on leprosy, AIDS and pyelonephritis.